The research project concerns a psychological investigation into the syntactic productivity of phrasal idioms. Its goal is to experimentally demonstrate that the syntactic productivity of idioms is largely predictable from their internal semantics. My aim is to predict which phrasal idioms in English will be viewed as syntactically productive. The main hypothesis considered is that speakers make assumptions about the way in which parts of idioms contribute to their interpretations as a whole, which should affect their intuitions of the syntactic versatility of these figurative phrases and the processes used in comprehending idioms. The first series of experiments looks at the interpretation of phrasal idioms when syntactically and semantically altered to assess people's intuitions about the syntactic behavior of idioms. The second series of studies uses "on-line" information processing techniques to examine the moment-by-moment processes used when people understand idiomatic phrases. The results of these studies should demonstrate that idioms do not form a unique class of linguistic items (e.g., as "dead" metaphors), but can share many of the same compositional properties normally associated with more "literal" language. Most significantly, this research should help intergrate the work on figurative language processing with more mainstream research on cognitive psychology on sentence comprehension. These studies should also provide valuable information for mental health professionals interested in the interpretation of figurative language by patients with various mental health disorders.